on certain heavily-trafficked motorways some deterioration of the surfacing, particularly in the nearside lane, has occurred as a result of the continual increase in the number of vehicles and of the average axle load. this report describes the laying of five experimental surfacings on the m1 motorway near watford gap. the surfacings comprise a pervious macadam designed to reduce spray from vehicles when the road is wet and four rolled asphalts with an improved resistance to deformation. all the surfacings are designed to have a high resistance to skidding. two control sections of rolled asphalt have been included for comparison. the effect of build-up of black deposits which sometimes occur after long dry spells of weather will be observed. (a)